Should I be planking on my forearms or my hands? We asked Scarlett Johansson’s trainers

Pretty much every plank I’ve ever done has been on my forearms. Whether it’s during a fitness class or while watching one of my beloved online workout videos, I hold those suckers until I shake. At a recent Pilates class, however, the instructor asked me to spend a minute on my hands. I thought, “This is tough. Have I been cheating?” I couldn’t help but wonder, what’s the best method and how do I find proper plank form?

Each plank hurts in its own way. But having only ever used my forearms for support, switching it up had me all sorts of awkward and wobbly as a different set of muscles felt the burn. It turns out that by only sticking to one variation, I’ve been missing out on some serious arm-toning benefits. According to Eric Johnson and Ryan Johnson—brothers, personal trainers to Scarlett Johansson and Ryan Gosling, and founders of HOMAGE—both methods are effective, but they help accomplish totally different things for your body.

“The most effective plank variation is the one that’s right for your current fitness level and specific intention,” Eric says. “Performing planks on the hands is more challenging for the shoulders and triceps while performing the exercise on the forearms is more demanding for the core.”

Since hand and forearm planks target different muscle groups, there’s good reason to integrate both of them in your routine. Here’s how to make sure you’re performing each variation properly.

Hand plank

What it works: shoulders and triceps

How to do it: “Set up with your hands shoulder width apart and feet touching. Begin to ‘dial’ out your hands by trying to rotate your elbows in and turning your hands out. At this point, you should feel your lats contract as your shoulders depress and externally rotate,” Ryan explains. “Continue to radiate tension by spreading your fingers as much as possible and pressing through the floor and up into your shoulder girdle. As you press away from the floor, put your spine into a neutral position by tucking your ribcage and pelvis in a hollowed body position. Finally, contract your quads and glutes as hard as you can, creating total body tension.”

As you’re holding a plank, Ryan says it’s also important to focus on your breathing. Breathe in through your nose deep down into your diaphragm, then slowly exhale through your mouth.

As you’re holding your plank, Ryan says to focus on your breathing just like you would while performing the hands version. Inhale through your nose, allowing your diaphragm to expand, then exhale through your mouth.

How to build up your strength over time

As with all things, practice makes perfect when it comes to mastering planks. Whether you’re a planking newbie or want to “level up,” as Eric put it, get into plank position two to four times per week for two to five sets (10 to 60 seconds each) per workout.

“The goal isn’t to ‘survive’ the plank, but to maximize tension during the exercise. Basically, make it difficult for yourself: You should be shaking,” he says. “Do them at the beginning of your workout to act as a warm-up for the work ahead, or near the end of your workout—after your main strength movements—to increase the difficulty since you’re in a fatigued state.”